CVD plasma reactor

ABSTRACT

Chemical vapor deposition on a semiconductor wafer is obtained in a plasma reactor having a plurality of lamps for radiantly heating the wafer. Calibrated temperature sensing means remote from the wafer is used to control the heating of the wafer. Gases are supplied by way of a plurality of tubes extending radially inwardly from the sides of the chamber. A baffle is provided to form an antechamber which aids in the uniformity of the deposition. The plasma is ignited for less than the whole deposition cycle for deposition of tungsten disilicide.

BACKGROUND OF THE INVENTION

This invention relates to plasma treatment of an article and, inparticular, to plasma enhanced chemical vapor deposition (CVD).

The use of plasma reactors for various etching processes is well knownin the art. Also known, but less frequently exploited, is the use ofplasma reactors for deposition, e.g. a conductive or insulating layer ona semiconductor wafer. While the advantages of planar plasma reactorsare well known, e.g. U.S. Pat. No. 4,223,048, they are not free fromproblems. Some problems are inherent in the process itself. For example,silane (SiH₄) deposits silicon everywhere, once a minimum temperature isreached. The contamination problems are obvious. Silicon tetrachloride(SiCl₄) will not deposit silicon by itself and has a higher minimumdeposition temperature. Intermediate compounds, e.g. dichlorosilane(SiH₂ Cl₂), have intermediate characteristics. Thus, one is faced withthe problem of switching or mixing gases during a process, yet trying toobtain consistent results.

Another source of difficulty, in a sense, is the semiconductor industryitself. There is a constant demand for better results, e.g. uniformity,through-put, deposition rate. Improving both uniformity and depositionrate, for example, is not easy. Further, there are several kinds ofuniformity. A first relates to the wafer itself. A second concerns fromwafer to wafer in a given batch. A third kind relates to uniformity frombatch to batch. For single wafer plasma reactors, the latter two are thesame since the wafers are processed singly. As can be seen, improvingone parameter may not be particularly difficult. Improving all of themis a feat.

Another consideration is the increased use of automation. As known, itis highly desirable to process a plurality of wafers at a time in avacuum. Thus, vacuum load locks and vacuum transports are being usedmore frequently. This leads to the desire to process wafers morequickly, e.g. at higher deposition rates, to match more closely theincreased speed of the wafer transports. Thus, not only must the processbe improved, but the chamber in which the process takes place must becompatible with vacuum load locks and transports as well.

In view of the foregoing, it is therefore an object of the presentinvention to provide improved plasma deposition apparatus.

Another object of the present invention is to provide an improved plasmadeposition process in which both deposition rate and uniformity areimproved for single wafer deposition in an automated vacuum load lockconvertible for wafer diameters of 3-10 inches.

A further object of the present invention is to provide improved meansfor heating a semiconductor wafer.

A further object of the present invention is to provide improved meansfor controlling gas flow in a deposition chamber.

Another object of the present invention is to provide improvedtemperature sensing means for deposition apparatus.

A further object of the present invention is to provide improved controlmeans for radiantly heating a wafer.

Another object of the present invention is to provide a process chambercompatible with vacuum transport apparatus.

SUMMARY OF THE INVENTION

The foregoing objects are achieved in the present invention wherein aplasma reactor comprises a chamber having an annular baffle positionedto divide the chamber into an antechamber and a reaction chamber.Positioned about the periphery of the reaction chamber are gas supplyand exhaust ports. The gas supply ports include extenders which projectradially inwardly. An annular wall extends from the baffle into thereaction chamber. The extenders pass through the wall and are supportedthereby. The baffle is separated from the periphery of the chamber by agap. The baffle comprises a central aperture. Gases can circulatebetween the antechamber and the reaction chamber through the gap and theaperture.

The wafer is held on a quartz window to which a heater means isattached. The heater comprises lamps resiliently mounted on a conductivemember but electrically isolated from the conductive member.

Temperature sensing means are mounted in the conductive member on theopposite side of the lamps from the wafer.

The process is based upon the discovery that the plasma impedesdeposition. In accordance with the present invention, the plasma isignited for less than the whole deposition cycle.

In the process, the wafer is brought up to a predetermined temperatureby applying full power to the lamps. At a predetermined temperature, asdetected by the temperature sensor and related circuitry, the power tothe lamps is reduced to an amount sufficient to maintain the temperatureof the wafer. The deposition gas is supplied to the chamber and a plasmais ignited. The plasma is terminated and the deposition continues. Aftera predetermined length of time the deposition gas is stopped and thelamps are turned off. The wafer is then cooled and removed.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention can be obtainedby considering the following detailed description in conjunction withthe accompanying drawings, in which:

FIG. 1 illustrates a deposition chamber in accordance with the presentinvention.

FIG. 2 illustrates a portion of the temperature sensor in accordancewith the present invention.

FIG. 3 illustrates a portion of the baffle and extenders in accordancewith the present invention.

FIG. 4 illustrates the orientation of the extenders in accordance withthe present invention.

FIG. 5 illustrates an alternative embodiment of a deposition chamber inaccordance with the present invention.

FIG. 6 illustrates a deposition process in accordance with the presentinvention.

FIG. 7 illustrates a gas deposition characteristic used in the presentinvention.

FIG. 8 illustrates temperature sensing in accordance with the presentinvention.

FIG. 9 illustrates control circuitry in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a preferred embodiment of a reactor chamber forplasma enhanced chemical vapor deposition. In accordance with thepresent invention two chambers separated by a baffle are provided inwhich the reactor chamber, containing the semiconductor wafer, isseparated from the antechamber, wherein the plasma is generated, by anaperture smaller than the diameter of the wafer.

In particular, reactor 10 comprises an upper electrode 11 which isattached to insulating member 12 by suitable means, not shown.Insulating member 12 preferably comprises an annular ring having grooveson each major surface thereof for receiving a suitable sealing member,such as an O-ring. Insulating member 12 is mechanically connected toconductive member 13 which also preferably comprises an annular ring.Conductive member 13 contains the gas supply and exhaust lines, asfurther described herein, and suitable cooling means, well known per seto those of skill in the art. Members 12 and 13 form the sidewall of thereactor and need not be the same thickness. Typical thicknesses, for areactor for depositing on four inch diameter wafers, are 0.5 inches forinsulating member 12 and 0.5 inches for conductive member 13. Thecentral apertures of each of these members are typically six inches indiameter, for a four inch diameter wafer, although they need not beidentical.

Within the space defined by conductive member 13, is baffle means 14which comprises a generally planar portion 2 and an annular wall portion3. Planar portion 2 is separated from conductive member 13 by apredetermined distance 4, e.g. 100 mils. Wall 3 is separated fromconductive member 13 by a predetermined distance, typically 300 mils,for a system depositing layers on four inch wafers. As with the otherdimensions given herein, the height of annular wall 3 depends upon thesize and geometry of chamber. A height of 0.5 inches has been foundsuitable for a chamber depositing layers on four inch wafers.

Conductive member 13 comprises a plurality of gas supply and exhaustports, more fully illustrated in FIG. 3. Connected to the gas supplyports are extenders such as extender 15 as illustrated in FIG. 1.Extender 15 is connected to conductive member 13 and extends through asuitably sized bore in wall 3. Planar portion 2 of baffle 14 comprisesan aperture 17, e.g. having a diameter of 3 inches and approximatelycentered therein. As thus constructed, reactor 10 comprises anantechamber 16 and a reactor chamber 18 which contains wafer 19. Thesechambers communicate by way of aperture 17 and gap 4 about the peripheryof baffle 14.

Wafer 19 rests upon a thermally translucent or transparent, insulatingmember 21, which preferably comprises quartz, held in place by frame 22.Insulating member 21 serves to close chamber 18 about wafer 19. Member21 also provides a window through which wafer 19 can be radiantlyheated.

The radiant heating portion of reactor 10 comprises a plurality of lamps24, 25 and 26 mounted on a cup-shaped, conductive member 23 which servesto enclose the lamps and contains suitable passageways for the supplyand exhausting of a cooling gas or air. Lamps 24-26 preferably comprisehalogen lamps, which are rich in infrared radiation, such as ANSI typeDXW, a 120 volt 1000 watt lamp. In a preferred embodiment of the presentinvention, there is a fourth lamp, not shown, positioned opposite lamp25 and in a generally symmetrical relationship with the other lampsabout the center of the chamber. Lamps 24-26 are resiliently mounted bymeans of angle bracket means 31 and attached to insulating feedthroughmember 32 by way of conductive bolt 33. Cup 23 is preferably gold platedto increase the reflection of infra-red radiation.

As thus constructed, the lamps are attached securely to conductivemember 33 but yet are resiliently mounted so that, during theconsiderable expansion the lamps undergo when turned on, reliablecontact is made to the lamps without compressively stressing the lamps.Insulating feedthrough 32 serves to isolate the power applied to thelamps from cup 23.

Mounted within cup 23, but thermally isolated from cup 23, isthermocouple 39 which is mounted on a small disk of predetermined massto simulate the mass of wafer 19. During a typical process run, asilicon wafer must be heated to and kept at a temperature ofapproximately 400° C. Direct monitoring and control of this temperatureis very difficult due to the presence of reactive gases, a highfrequency electric field, and the need to maintain a good vacuum seal.In accordance with the present invention, thermocouple 39, mounted on adisk of predetermined mass, simulates the heating of the wafer andprovides a relatively simple means for monitoring and controlling thetemperature of the wafer.

FIG. 2 illustrates in greater detail the construction of the temperaturesensor in accordance with the present invention. Thermocouple 39 isattached to disk 40 which comprises, for example, anodized aluminum,ceramic, or graphite. In general, disk 40 can comprise any lowreflectance, low specific heat material. Disk 40 is thermally isolatedfrom fitting 48 by a plurality of pins, such as pin 49, and is dimpledto facilitate locating the disk on the pins. Disk 40 is surrounded bythermally transparent tube 48a which isolates disk 40 from the coolingair for the lamps. Tube 48a extends to, but does not touch, window 21.Approximately centrally located in fitting 48 is tube 48b, which conveyscooling air to disk 40. This air is not continuously provided and isreferred to as "reset air" to distinguish it from the air for coolingthe lamps. As more fully described herein, the reset air is used tobring disk 40 to a reference temperature. Once the temperature isachieved, the process cycle can begin and, when begun, the reset air isshut off so that disk 40 can increase in temperature.

Thermally transparent tube 48a preferably comprises quartz and tube 48bpreferably comprises stainless steel. Tube 48b conveniently providesaccess for the leads to thermocouple 39 and a means for spring-loadingdisk 40 to hold it in place against pins 49. As more fully describedherein, the choice of thermocouple depends upon the temperature range ofdisk 40. Typical materials include chromel-alumel andplatinum-platinum/rhodium.

In accordance with the present invention, upper electrode 11 isconnected to source 5 of RF power, e.g. up to several hundreds watts ata frequency of 13.56 MHz. It is understood by those of skill in theplasma deposition art that other frequencies and power ranges may beused. Conductive member 13 is preferably grounded, thereby reducing thetendency for plasma discharge to enter the supply or exhaust lines.

FIG. 3 illustrates a portion of the baffle extenders in accordance withthe present invention. Specifically, conductive member 13 has extender15 fastened thereto and passing through a suitable hole in wall 3 ofbaffle 14. A plurality of holes such as holes 42 and 43 are providedapproximately regularly about wall 3 to assure relative uniformity inthe distribution of gases within the chambers. Similarly, exhaust ports45 and 46, and others, are preferably uniformly distributed about theinterior face of conductive member 13. Extender 15, and the otherextenders, comprise hollow tubes having sealed ends and bores in theupper portion thereof for releasing the gas within chamber 18, away fromwafer 19, and within aperture 17. This is believed to improve the mixingof the gases and improves the uniformity of the deposition on wafer 19.

As illustrated in FIG. 4, the extenders are not all of the same lengthbut are varied in length to improve the uniformity of the deposition. Asillustrated in FIG. 4 two adjacent extenders, 51 and 52, are of unequallength and comprise one pair of several pair extending radially inwardlyfrom wall 3 on baffle 14. While illustrated as having this particularpattern in FIG. 4, it is understood by those of skill in the art thatvarious other configurations can be employed. For example, extenders ofthree different lengths could be used or extenders of two differentlengths could be arranged in bilaterally symmetrical groups of fours.

As illustrated in FIG. 5, the reactor of the present invention can beinverted to accommodate various wafer transport systems for automaticprocessing of wafers. To accomplish this, a portion of the reactor ismovable to provide clearance for the transport. Specifically, thereactor is split at lamp housing 60 which is fixed and forms the upperpart of the chamber. The remainder of the chamber is lowered so that awafer can be inserted, e.g. by a spatula from the transport mechanism(not shown). The reactor of FIG. 5 contains all the elements shown inFIG. 1, although several are omitted from the figure for the sake ofsimplicity. The principal difference between FIGS. 1 and 5 is the use oftines 67, 68 to hold wafer 19 against the window in lamp housing 60. Theactual number of tines is not critical, although at least three arenecessary to hold the wafer.

When reactor chamber and antechamber are lowered, as indicated by thedotted lines, tines 67 and 68 extend upwardly, above the sealing plane,so that the wafer can be placed or retrieved by the transport mechanism.When the chambers are raised, wafer 19 is held tightly against thewindow so that deposition occurs on the lower side of the wafer. Thetines are cantilever mounted in the wall of the chamber and extendacross the edge of wafer 19 only far enough to assure reliable wafertransfers. Inverted operation reduces contamination on the wafersurface.

The operation of the plasma reactor in accordance with the presentinvention may better be understood by considering FIG. 6 in which theheating and plasma discharge times are illustrated. During thedeposition cycle, wafer 19 is heated to a predetermined temperature asillustrated by curve 55. Once that temperature is achieved, for exampleapproximately 400° C., the power applied to lamps 24-26 is reduced tomaintain wafer 19 at a relatively uniform temperature. During this timea glow discharge is ignited within the antechamber to provide reactivespecies which contact wafer 19 and initiate the deposition cycle. It hasbeen found that the plasma discharge appears necessary toinitiate/nucleate deposition but detrimental to the continuation ofdeposition of tungsten disilicide. In accordance with the presentinvention the glow discharge is terminated after a predetermined lengthof time illustrated in FIG. 6 by cross-hatched area 59. The depositionprocess continues, however because wafer 19 is maintained at atemperature above the dissociation temperature of the reactive gases.After a further predetermined length of time, determined in part by thedesired thickness for the deposited layer, the applied power to lamps24-26 is reduced to zero and wafer 19 is permitted to cool asillustrated by curve 58.

The control of the temperature of the wafer is made less critical, inaccordance with the present invention, by choosing a suitable depositiontemperature above a predetermined minimum. As illustrated in FIG. 7 thedeposition rate in a given process is temperature dependent. It has beenfound that the temperature dependency follows an Arrhenius plot; i.e.deposition is proportional to e (the natural logarithm base) raised to apower of the negative reciprocal of the absolute temperature. The slopeof this curve is proportional to the apparent activation energy for thisreaction. The curve can be generalized as a first line having arelatively shallow slope such as line 61, and a second line having aconsiderably steeper slope such as illustrated by line 62. In accordancewith the present invention, one maintains the temperature of wafer 19above temperature T_(c) as illustrated in FIG. 7 wherein the depositionrate varies gradually with temperature change. Thus one obtains a systemin which the control of temperature, while important, is not criticalfor film thickness control so long as a minimum deposition temperatureis exceeded.

The control of the temperature of the wafer is not quite as idyllic asrepresented in FIGS. 6 and 7. FIG. 8 illustrates the temperatures asseen by wafer 19, in the upper curve, and as seen by thermocouple 39, inthe lower curve. The process in accordance with the present inventioncan best be understood by considering FIGS. 1, 6 and 7 together.

Since heat and temperature are thermodynamically separate entities,maximum precision is obtained in accordance with the present inventionwhen wafer 19 and sensor 39 begin the process cycle at knowntemperatures. Wafer 19 is typically at room temperature, 20° C. Sensor39 is brought to a predetermined temperature by the application of resetair, previously described. When this temperature is achieved, aninitial, low power is applied to lamps 24-26 to warm the lamp filamentsand minimize the inrush current. After a brief period of time, e.g. twoseconds, full power is applied to lamps 24-26 to bring wafer 19 up todeposition temperature. This is illustrated in FIG. 6 by curve 55 and isillustrated in FIG. 8 by curves 63 and 73.

Wafer 19 and disk 40 are both radiantly heated by lamps 24-26, theinfrared energy of which is readily passed by quartz window 21 to wafer19. Wafer 19 absorbs a substantial fraction of the incident energy andincreases in temperature, as does disk 40. When a predetermined wafertemperature is achieved, e.g. 390°-400° C., the power applied to lamps24-26 is reduced to a predetermined lower level sufficient to sustainthe temperature of wafer 19.

As illustrated in FIG. 8, the temperature seen by thermocouple 39 dropssubstantially, as illustrated by curve 64, and then stabilizes at alower temperature as illustrated by curve 65. The temperature of thedisk drops due to radiant cooling and, to some extent, due to thecooling of lamps 24-26 by way of air or gas flowing through passageways35. The temperature of wafer 19, on the other side of the window, ismaintained at a relatively uniform level as illustrated by curve 75.Data for the curves illustrated in FIG. 8 have been obtained bysubstantial experiments wherein the temperature of the wafer wasmeasured directly by a plurality of probes during the calibration ofsensor 39.

The ratio of the temperature represented by the upper curve in FIG. 8 tothe temperature represented by the lower curve in FIG. 8 depends upon anumber of factors. Among these are the location, mass, reflectance, andspecific heat of disk 40 as well as the process being run. By choice ofmaterial for disk 40, one can eliminate the peak formed by curves 63 and64 and/or raise the level of curve 65.

Raising the temperature of disk 40 relative to wafer 19 has thetheoretical effect of improving temperature control. For example, asillustrated in FIG. 8, a five degree error in disk temperature (curve65) could amount to a ten or twelve degree error in wafer temperature(curve 75). If the disk temperature were higher than the wafertemperature, the error would be reduced. If graphite were used for disk40, the temperature of the disk would go much higher during the processcycle than it does for an aluminum disk, even higher than thetemperature of the wafer. However, the thermocouple material should alsobe changed, e.g. to platinum-rhodium/platinum, which tolerates highertemperatures but has a smaller temperature coefficient of resistancethan chromel-alumel. Thus, the improvement is not as great as one mightexpect.

A reactive gas, e.g. dichlorosilane, is supplied by way of conductivemember 13 and extenders 15 to reactor chamber 18. The gas alsocirculates through antechamber 13 wherein a plasma discharge isinitiated. The supplied gas as well as gaseous by-products are exhaustedby way of the ports in conductive member 13 positioned outside wall 3.Thus the flow in the chambers is broadly describable as a radial flowfrom the central portion to the periphery. As known per se in art, thedichlorosilane dissociates in the presence of heated wafer 19 to depositsilicon thereon. The plasma discharge serves to initiate the depositionof silicon.

Not only does the gas flow from a central area to the periphery, but theelectric field lines do also. In general, the field diverges from upperelectrode 11 to conductive member 13. This divergence reduces radiationdamage to sensitive devices such as thin gate oxides. Despite thedivergence of the field and of the gases, good uniformity is obtained.This is believed due in part to adjustment of the gas distribution andto the compactness of the chamber, approximately one half liter involume for four inch wafers. Typical single wafer plasma reactors have avolume of five to seven liters. Ions traveling from the antechamber tothe wafer do not have far to go in the chamber of the present invention.

FIG. 9 illustrates a circuit in which temperature sensing means,separated from the wafer by a window, produces a signal representativeof the temperature of the wafer. Transducer means converts the signal todigital form and control means, connected to the lamps, regulate thepower dissipated by the lamps in accordance with the digital signal.

The temperature of the wafer is simulated by thermocouple 39 and disk 40as previously described. Thermocouple 39 is connected to operationalamplifier 81 which provides suitable amplification and linearizationcharacteristics for the thermocouple. Operational amplifier 81 isconnected to threshold sensing amplifiers 82 and 83. Amplifiers 82 and83 preferably include at least some hysteresis to prevent noise fromcausing the lamps to be energized intermittently. Comparator 82 is alsoconnected to a source of variable voltage illustrated by potentiometer84. Similarly comparator 83 has another input thereof connected to asource of variable voltage illustrated in FIG. 9 as potentiometer 85.Potentiometers 84 and 85 set the threshold sensed by comparators 82 and83, respectively.

In operation, comparators 82 and 83 compare the voltage levels at theinputs thereof and produce an output signal indicative of which inputhas the greater voltage. One thus obtains a binary representation of thetemperature sensed by thermocouple 39. This binary representation isapplied to the inputs of a suitable microprocessor, illustrated in FIG.9 has CPU 91. CPU 91 has an output thereof, illustrated as data bus 92,connected to an interface circuit 93 which provides the necessaryisolation between CPU 91 and control circuit 94. Interface circuit 93also contains zero crossing detectors for providing a signal to controlcircuit 94 which is synchronized with zero crossings of the A.C.powerline. Thus one can control power to the lamps by synchronousswitching of half cycles of the applied power and can pick turn-onpoints with respect to zero crossings in the powerline. Control circuit94 comprises devices such as silicon controlled rectifiers for switchinghigh voltages and currents from a suitable source of power 95 to lamps101 and 103.

Electrical components corresponding to the elements illustrated in FIG.9 are well known per se to those of skill in the art and may oftencomprise but a single semiconductor device.

In operation the switching thresholds are set by potentiometers 84 and85. The output from thermocouple 39 is amplified and linearized byamplifier 81 and applied to the other inputs of comparators 82 and 83.During the initial phase of the process, thermocouple 39 is cooled to apredetermined initial temperature as indicated by potentiometer 84. Whenthis temperature is reached, the output from comparator 82 changesstate, which change of state is sensed by CPU 91. CPU 91 then provides asignal to control circuit 94 by way of interface circuit 93 to turn onlamps 101 and 103 a predetermined amount.

After the lapse of a predetermined time, CPU 91 directs controller 94 toprovide full power to lamps 101 and 103. Meanwhile, the temperature atthermocouple 39 is continuously monitored by comparators 82 and 83 whichprovide temperature setpoints to CPU 91. When CPU 91 receives a signalfrom comparator 83 indicating that the predetermined depositiontemperature has been obtained, CPU 91 directs controller 94 to provide areduced amount of power to lamps 101 and 103. Other inputs, not shown,to CPU 91 control the timing thereof, e.g. the duration of the processcycle. At the termination of the process cycle, CPU 91 directscontroller 94 to remove power from lamps 101 and 103, thereby allowingwafer 19 to cool. During the cooling phase, an inert gas is provided tochambers 16 and 18 to enhance the cooling of wafer 19. Chambers 16 and18 and then restored to atmospheric pressure so that wafer 19 can beremoved.

As a specific example of the present invention, amorphous silicon wasdeposited at the rate of 0.09 microns per minute from dichlorosilane ata pressure of 200 millitorr at a flow of 92 SCCM at 500° C. with anapplied RF power of 150 watts for 60 seconds. The deposited film had athickness of 900 angstroms, an infinite resistivity, and a uniformityacross the wafer of ±2.5%.

A second specific example of the present invention is deposition oftungsten disilicide from a mixture of dichlorosilane and tungstenhexaflouride at a rate of 2000 angstroms per minute, at a pressure of150 millitorr, at a flow of 50 SCCM of dichlorosilane and 2.8 SCCM oftungsten hexaflouride at 450° C. The deposition film had a thickness of2000 angstroms for a 60 second run, a deposited resistivity of 300 μΩcm,a reflectivity of 50% at 5500 angstroms and a thickness uniformity of±5%. The plasma was terminated after about 15 seconds. Thus, the plasmais used only to initiate or to nucleate the layer of tungstendisilicide.

There is thus provided by the present invention a substantially improvedplasma reactor for the chemical vapor deposition of various materials.The wafer is efficiently heated radiantly and the temperature of thewafer is simulated to provide control of the deposition. The control oftemperature and gas uniformity and the internal baffle of the reactorassure good uniformity of the deposited layer. In addition, a rapiddeposition is obtained.

Having thus described the invention it will be apparent to those ofskill in the art that various modifications can be made within thespirit and scope of the present invention. For example, while reactor 10preferably comprises stainless steel for the conductive members andquartz for the insulating member other materials can be used such asInconel, graphite, or ceramics. Since programmable logic is used, otherfeatures can be added, e.g. a test for filament continuity can be easilymade. A failure of this test would cause the process to terminate sincethe deposition would be uneven. While the sustaining power level ispre-programmed, one can readily add another threshold sensor and controlthe temperature dynamically with CPU 91 in a feedback loop. Whileillustrated as connected in parallel with a single control circuit, itis understood that each lamp may require its own control circuit due tothe high power dissipation of the lamps.

We claim:
 1. Chemical vapor deposition apparatus comprising:means forenclosing a predetermined volume; baffle means for dividing said volumeinto two chambers; RF means coupled to a first of said chambers forgenerating a plasma therein, the second of said chambers for containingan article upon which a deposit is to be formed out of contact with saidplasma; heating means for directly heating said article by radiantenergy; and wherein said enclosing means comprise window means forproviding a transmission path from said heating means to the interior ofsaid second chamber; said heating means being on the outside of saidwindow means.
 2. The apparatus as set forth in claim 1 wherein saidbaffle means comprises a central aperture through which gases can flowfrom one chamber to the other.
 3. The apparatus as set forth in claim 2wherein said enclosing means comprises:a first conductive member; agenerally planar non-conductive member of predetermined thickness; asecond conductive member of predetermined thickness; wherein said secondconductive member and said non-conductive member each having a hollowcentral portion defining said volume.
 4. The apparatus as set forth inclaim 3 wherein said baffle means is positioned in or near the plane inwhich said non-conductive member and said second conductive member meet.5. The apparatus as set forth in claim 1 wherein said baffle comprises aplanar, annular ring of diameter less than the diameter in which it isplaced, thereby forming a gap between the periphery thereof and saidenclosing means.
 6. The apparatus as set forth in claim 5 wherein saidsecond conductive member comprisesa plurality of gas supply and gasexhaust passageways which extend through the bulk of said member to theinterior surface thereof which defines said hollow central portion. 7.The apparatus as set forth in claim 6 and further comprising:extendermeans, attached to the gas supply passageways of said second conductivemember, for supplying gas to the interior of said volume.
 8. Theapparatus as set forth in claim 7 wherein an extender means is attachedto each supply passageway wherein it intersects said second conductivemember.
 9. The apparatus as set forth in claim 8 wherein said firstchamber is an antechamber and said second chamber is a reaction chamber,said baffle further comprising:wall means extending from said baffleinto said reaction chamber to homogenize the effects of gas flow ofpumping through said exhaust passageways.
 10. The apparatus as set forthin claim 9 wherein said wall means comprises a plurality of aperturesand said extender means pass through said apertures to reach theinterior of said volume.
 11. The apparatus as set forth in claim 10wherein said extender means each comprise a tube having at least oneaperture on the side thereof.
 12. The apparatus as set forth in claim 11wherein said apertures face away from said article.
 13. The apparatus asset forth in claim 9 wherein said wall is located a predetermineddistance from the periphery of said ring.